One type of agricultural machine is a harvesting machine, e.g., an agricultural combine. Agricultural combines are engine powered machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger.
Such harvesting machines typically include a cooling package to remove heat from the coolant circulating through the engine powering the agricultural combine. The cooling package may include, for example, a housing mounting a radiator, and a rotary screen mounted on the air intake side of the radiator. Due to the presence of dust and chaff during operation of the agricultural combines, the rotary screen begins to collect the dust and chaff on the outer surface of the rotary screen. A vacuum duct is used to transfer the material, e.g., dust and chaff, off of the outer screen surface of the rotary screen during operation, with the vacuum source being provided by the engine cooling fan associated with the cooling package.
In addition, many harvesting machines also use a pre-cleaner to prevent large dust and crop material from entering the air filter system, thereby increasing air filter life. The material separated by the pre-cleaner must be removed from the pre-cleaner device. One way to remove the material separated by the pre-cleaner is to aspirate this material captured by the pre-cleaner to the exhaust stack through a venturi. However, an exhaust venturi may cause excessive back pressure in the engine exhaust system, and the pressure drop created by the exhaust venturi is heavily dependent on engine load. Another way to remove the material separated by the pre-cleaner is to aspirate by utilizing the pressure drop created by the engine cooling fan.
Such designs that utilize the pressure drop created by the engine cooling fan are dependent on engine load, and thus at times may be inconsistent in cleaning the cooling package air screen and aspirating the air cleaner pre-cleaner.